Long-term outcomes after endoscopic removal of malignant colorectal polyps: Results from a 10-year cohort

BACKGROUND

Choosing an optimal post-polypectomy management strategy of malignant colorectal polyps is challenging, and evidence regarding a surveillance-only strategy is limited.

AIM

To evaluate long-term outcomes after endoscopic removal of malignant colorectal polyps.

METHODS

A single-center retrospective cohort study was conducted to evaluate outcomes after endoscopic removal of malignant colorectal polyps between 2010 and 2020. Residual disease rate and nodal metastases after secondary surgery and local and distant recurrence rate for those with at least 1 year of follow-up were investigated. Event rates for categorical variables and means for continuous variables with 95% confidence intervals were calculated, and Fisher's exact test and Mann-Whitney test were performed. Potential risk factors of adverse outcomes were determined with univariate and multivariate logistic regression models.

RESULTS

In total, 135 lesions (mean size: 22.1 mm; location: 42% rectal) from 129 patients (mean age: 67.7 years; 56% male) were enrolled. The proportion of pedunculated and non-pedunculated lesions was similar, with en bloc resection in 82% and 47% of lesions, respectively. Tumor differentiation, distance from resection margins, depth of submucosal invasion, lymphovascular invasion, and budding were reported at 89.6%, 45.2%, 58.5%, 31.9%, and 25.2%, respectively. Residual tumor was found in 10 patients, and nodal metastasis was found in 4 of 41 patients who underwent secondary surgical resection. Univariate analysis identified piecemeal resection as a risk factor for residual malignancy (odds ratio: 1.74; P = 0.042). At least 1 year of follow-up was available for 117 lesions from 111 patients (mean follow-up period: 5.59 years). Overall, 54%, 30%, 30%, 11%, and 16% of patients presented at the 1-year, 3-year, 5-year, 7-year, and 9-10-year surveillance examinations. Adverse outcomes occurred in 9.0% (local recurrence and dissemination in 4 patients and 9 patients, respectively), with no difference between patients undergoing secondary surgery and surveillance only.

CONCLUSION

Reporting of histological features and adherence to surveillance colonoscopy needs improvement. Long-term adverse outcome rates might be higher than previously reported, irrespective of whether secondary surgery was performed.

Overexpression of α1 chain of type XI collagen (COL11A1) aids in the diagnosis of invasive carcinoma in endoscopically removed malignant colorectal polyps

INTRODUCTION

The histologic distinction between benign misplaced adenomatous mucosa and invasive adenocarcinoma in colorectal polyps can be challenging. The α1 chain of type XI collagen (COL11A1) has been shown to be overexpressed in cancer-associated stromal fibroblasts. The aim of this study was to investigate the operating characteristics of COL11A1 immunostaining in benign and malignant colorectal polyps as a potential diagnostic aid.

MATERIALS AND METHODS

Sixty-six endoscopically-removed paraffin-embedded colorectal polyps were stained with anti-COL11A1 antibody. They comprised 50 malignant polyps (MPs) with invasive adenocarcinoma (including 5 with concurrent benign misplaced adenomatous mucosa) and 16 adenomas, 11 with and 5 without benign misplaced adenomatous mucosa.

RESULTS

COL11A1 was expressed either diffusely or focally in cancer-associated desmoplastic fibroblasts in 72.0% (36/50) of MPs. The rates of COL11A1 expression and the immunohistochemical staining patterns of the COL11A1 were positively correlated with the depth of cancer invasion in MPs. COL11A1 was expressed in all 9 (100%) MPs with a mucinous component and in 16/18 (88.9%) MPs associated with significant electrocautery effects. COL11A1 was not expressed adjacent to conventional adenomas or in the stroma adjacent to misplaced adenomatous mucosa.

CONCLUSIONS

COL11A1 antibody can assist in distinguishing the cancer-associated desmoplastic stroma from that associated with misplaced adenomatous mucosa. It is particularly helpful when electrocautery artifacts or mucin pools interfere with the diagnosis of invasive carcinoma. However, COL11A1 has limited value in diagnosing superfically invasive carcinomas with very little desmoplastic stroma due to its low positive rate and focal expression in some cases.